High-pressure fuel accumulator

ABSTRACT

A high-pressure fuel accumulator for a common-rail fuel injection system of an internal combustion engine has a tubular main body ( 1 ) to which is welded at least one bushing ( 13 ) for connecting a high-pressure line ( 6 ). 
     To improve the quality and safety of the high-pressure connections, a collar ( 14 ) is formed on the end of the bushing ( 13 ) facing the main body ( 1 ).

BACKGROUND INFORMATION

The present invention relates to a high-pressure fuel accumulator for acommon-rail fuel injection system of an internal combustion engine,having a tubular main body to which is welded at least one bushing forconnecting a high-pressure line.

A high-pressure fuel accumulator of this kind is described, for example,in European Patent Application 866,221 A1. In common-rail injectionsystems a high-pressure pump, possibly with the assistance of apre-supply pump, conveys the fuel to be injected from a tank into thecentral high-pressure fuel accumulator, which is known as the commonrail. Fuel lines lead from the rail to the individual injectorsassociated with the cylinders of the internal combustion engine. Theinjectors are controlled individually by the engine electronic system asa function of the operating parameters of the internal combustion engineto inject fuel into the combustion chamber of the internal combustionengine.

The object of the present invention is to improve the quality and safetyof the high-pressure connections in a high-pressure fuel accumulator ofthe type described in the preamble. In addition, the high-pressure fuelaccumulator according to the present invention should have a simpledesign and should be inexpensive to manufacture.

This object is achieved with a high-pressure fuel accumulator for acommon-rail fuel injection system of an internal combustion engine,having a tubular main body to which is welded at least one bushing forconnecting a high-pressure line, by the fact that a collar is formed onthe end of the bushing facing the main body.

ADVANTAGES OF THE INVENTION

The collar is used for introducing the welding current required forwelding the bushing. In the case of conventional bushings without acollar, the welding electrode is applied to the end of the bushingfacing away from the main body. In this case, welding splashes can enterthe interior of the bushing and can damage a thread provided there. Inaddition, the geometry in the interior of the bushing may be deformed inan unwanted manner due to the temperatures that occur in welding. Thesedisadvantages are avoided by providing the collar according to thepresent invention as a point of action for a welding electrode. Anotheradvantage is that the collar forms a point of action for a force whichpresses the bushing against the main body during welding. Such a forcecan practically also be applied with the welding electrode.

A special embodiment of the present invention is characterized in that abore leads from the interior of the tubular main body, opening into areceiving funnel which widens toward the outside and is used to receiveone end of the high-pressure line which is pressed against the receivingfunnel by an essentially hollow cylindrical press-screw so that it istight under high pressure, and the seal is surrounded by an essentiallyhollow cylindrical insulation ring. An electric shunt is reliablyprevented by the insulation ring when welding the bushing. In addition,the insulation ring prevents welding splashes from reaching the sealwhen welding the bushing.

Another special embodiment of the present invention is characterized inthat the insulation ring is premounted in the bushing, and the innerlateral surface of the insulation ring is in contact with the outerlateral surface of a projection in which the receiving funnel is formed.This yields the result that the bushing is centered relative to theprojection in assembly before welding.

Another special embodiment of the present invention is characterized inthat the end of the high-pressure line is designed in a ball shape, andthe inside diameter of the press-screw is larger than the outsidediameter of the high-pressure line. This permits a clearance of thehigh-pressure line relative to the bushing. This yields the advantagethat any installation tolerances in the engine compartment can becompensated.

Another special embodiment of the present invention is characterized inthat the end face of the bushing which faces the tubular main body istapered toward the inside. Due to this tapering, access to theconnecting point between the bushing and the tubular main body isfacilitated.

Additional advantages, features and details of the present invention arederived from the following description, in which two embodiments of thepresent invention are described in detail with reference to the drawing.The features mentioned in the claims and the description may beessential to the present invention either individually or in anycombination.

DRAWING

The drawing shows:

FIG. 1 a view of a cross section through a high-pressure fuelaccumulator according to a first embodiment of the present invention,and

FIG. 2 a view of a cross section through a high-pressure fuelaccumulator according to a second embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The high-pressure fuel accumulator shown in cross section in FIG. 1includes a tubular main body 1. A longitudinal bore 2 in tubular mainbody 1 is used to store the fuel which is under a high pressure. Aplurality of transverse bores, only one of which is shown in FIG. 1,namely transverse bore 3, lead away from longitudinal bore 2. Transversebore 3 opens outward in a receiving funnel 4. Receiving funnel 4 isdesigned in a conical shape and forms a sealing face for a spherical end5 of a high-pressure line 6. Spherical end 5 of high-pressure line 6develops into an area 7 having a widened outside diameter. A pressureshoulder 8 is formed on the outside of high-pressure line 6 followingarea 7 having a widened outside diameter.

A depression 9, which is formed on the inner circumference of the end ofa press-screw facing tubular main body 1, is in contact with pressureshoulder 8 of high-pressure line 6. Press-screw 10 has essentially theshape of a hollow circular cylinder through which high-pressure line 6passes. Press-screw 10 is provided with an outside thread 11 whichinteracts with an inside thread 12 formed in a hollow cylindricalbushing 13.

A collar 14 is provided on bushing 13 on the end facing tubular mainbody 1. A taper 15 is formed on the end face of bushing 13 which facestubular main body 1. Taper 15 is approximately perpendicular to adepression 19, which is formed on the inner circumference of bushing 13.At the interface between taper 15 and depression 19 there is aperipheral edge which is rounded and sits on a flattened surface 20which is formed on tubular main body 1. The connection between bushing13 and tubular main body 1 is formed by a weld 16.

A projection 17 is formed on tubular main body 1 at the center offlattened surface 20. Receiving funnel 4 is arranged at the center ofprojection 17. On the outside, projection 17 has the shape of a cylinderwhich is surrounded by an insulation ring 18. The insulation ring hasthe shape of a hollow circular cylinder which is fitted into bushing 13.

What is claimed is:
 1. A high-pressure fuel accumulator for acommon-rail fuel injection system of an internal combustion engine,comprising: a tubular main body; at least one bushing welded to the mainbody for connecting a high-pressure line; a collar situated on an end ofthe at least one bushing facing the main body; a receiving funnel, abore leading from an interior of the main body opening into thereceiving funnel, the receiving funnel widening toward an outside andbeing adapted to receive one end of the high-pressure line; asubstantially hollow cylindrical press-screw pressing the one end of thehigh-pressure line against the receiving funnel so as to be tight underhigh pressure; and a substantially hollow cylindrical insulation ringsurrounding a seal.
 2. The high-pressure fuel accumulator according toclaim 1, further comprising a projection in which the receiving funnelis formed, the insulation ring being premounted in the bushing, an innerlateral surface of the insulation ring being in contact with an outerlateral surface of the projection.
 3. The high-pressure fuel accumulatoraccording to claim 1, wherein the one end of the high-pressure line hasa ball shape, an inside diameter of the press-screw being larger than anoutside diameter of the high-pressure line.
 4. A high pressure fuelaccumulator for a common-rail fuel injection system of an internalcombustion engine, comprising: a tubular main body; at least one bushingwelded to the main body for connecting a high-pressure line; and acollar situated on an end of the at least one bushing facing the mainbody; wherein an end face of the bushing which faces the main body istapered toward an inside.